Project No. ZO1 NS 01523-08 DMN was incorporated in this project. Because of its scope, this is a long range study. According to conservative estimates for this country, over four million people are permanently handicapped by mental retardation (frequently of familial type), birth defects, progressive cerebral degeneration and inborn errors of metabolism. The Principal aim is to study the pathogenesis and etiology of these diverse disorders, to identify heterozygotes, and to institute therapeutic modification of the course of the respective diseases. The methodological approach includes clinical and genetic appraisal, tissue culture, enzymology, pathology and chemistry of lipidoses and mucopolysaccharidoses.